Gasoline inhibited against corrosion



United States PatentO 2,728,644 GASOLINE mnnsrrnn AGAINST CORROSION Samuel Clyde Vaughn, Berkeley, Calif., assignor to Tide Water Associated Oil Company, San Francisco, Calif., a corporation of Delaware No Drawing. Application April 1, 1952,

Serial Ne. 279,923

3 Claims. (Cl. 44-60) The present invention relates to corrosion inhibitors for gasolines having high octane ratings, arid especially those gasolines designed for use in aircraft type internal combustion engines. More particularly, it relates to cor rosion inhibitors formed as reaction products from alkyl acid phosphates and certain amines, and, which are compatible with other desirable additives. It further relates to anti-corrosive gasoline and means for producing the same. It also relates to the means for manufacturing corrosion inhibitors.

Recently, corrosion inhibitors for gasoline have attained importance as a result of research designed to inhibit corrosion in fuel systems and storage tanks, particularly where moist gasoline may come in contact with such metals as iron, copper, brass or the like. This type of corrosion is caused usually by the presence of water, and occurs generally at the water-gasoline interface. Furthermore, various components usedin leaded gasolines are thought to be active promoters of corrosion.

The appearance of water as a separate phase in aviation gasoline may be caused either by entrained water from the fueling pumps used in fueling aircraft, since these use water displacement to pump the gasoline; or, by moisture in the air above the gasoline in the fuel tank, since, at temperatures prevalent in high altitude flying, the moisture condenses and precipitates.

Another class of important additives often used in aviation gasoline is composed of certain anti-knock agents designed particularly for rich mixture operation. Foremost among these additives are aniline and its homologs, such as for example, ethyl aniline, methyl aniline, amyl aniline, diamyl aniline, cumidine, and xylidine. These aromatic amines are very effective for thisparticular purpose when used in proportions of about one to three percent of the gasoline, and function as cumene substitutes in aviation gasoline blends.

Although corrosion inhibitors and the above mentioned anti-knock agents-function excellently when each is used in the absence of the other, many of the common corrosion inhibitors are not compatible therewith. Consequently, when many of the alkyl acid phosphateamine neutralization products conventionally used for anti-corrosion purposes are added to a gasoline containing aniline or a homolog of aniline, an undesirable precipitate or haze forms. The deleterious effects of precipitates in liquid fuels are well recognized, and in this instance they may form a stoppage in carburetor jets or other fine orifices as well as remove a substantial portion of the corrosion inhibitor from the gasoline solution. It will-also be appreciated that gasoline homogeneity is one of the accepted requisites of marketability.

In accordance with the invention, it has been found that'when alkyl acid phosphates are reacted, or neutrali zed, with l-methyl, Z-heptadecyl, 4,5-dihydroimidazole; l-ethyl, 2 heptadecyl, 4,5-dihydroimidazole; or, l-propyl, 2 heptadecyl, 4,5 dihydroimidazole excellent gasoline soluble corrosion inhibitors are produced which do not form precipitates or haze in gasoline solutions containing aniline or its homologs.

While certain variations and deviations from the teachings of the present invention are encompassed within its scope and spirit, itis nevertheless recommended that the process of manufacturing the finished gasolines containing desired additives be carried'out in specified steps. For example, the order of addition of materials as well as the method of mixing the components must follow definite patterns.

The amine and alkyl acid phosphate may be reacted, or neutralized, by mixing the theoretical neutralizing quantities of the two components, heating above room temperature care being taken not to exceed temperature at which decomposition takes place, and then thoroughly mixing until reaction is complete. The reaction product is tested to determine the degree of neutralization, and after neutralization is confirmed as complete, said reaction product is then blended into gasoline as desired, or may be blended into a small amount of gasoline to be used as a gasoline concentrate. The aniline or homolog thereof may be added in whatever order desired. However, the amine-alkyl acid phosphate neutralization product is insoluble in aniline and its homologs and as a consequence thereof a one package additive is not practical.

Another procedure for manufacturing the novel reaction products which inhibit corrosion comprises dissolving the amine or gasoline concentrate of amine in the gasoline to be treated, and then adding a predetermined amount of alkyl acid phosphate. Alternately, the alkyl acid phosphate may be added to the gasoline and then the required amount of amine added. The blend is then mixed thoroughly for about a half-hour to insure complete reaction. A similar procedure may be followed for the preparation of a gasoline concentrate, should this be desired. The blend or concentrate is then tested for degree of neutralization, and when found to be satisfactory as evidenced by its non-precipitation or non-haze formation, the aniline or its homolog, or a gasolineconcentrate thereof, may then be added and the gasoline thoroughly mixed for ultimate use. I

It is an important qualification of the present process that the aniline or homolog thereof never be mixed with a blend containing the alkyl acid phosphate until all of the acidity of the alkyl acid phosphate has been neutralized by the amine. To test the degree of neutralization, the following procedure has been found to be effective. A drop of the reaction mixture is added tea 1% solution of aniline in aviation gasoline. If precipitation occurs on mixing then a small additional quantity of the. amine is added to thereaction mixture with con linued heating and agitation. This procedure is followed until a non-precipitating reaction product is finally formed from the alkyl acid phosphate and the dihydroimidazole. g

The alkyl acid phosphates which may be used in the neutralization step of the present process are those having from 8 to 16 carbon atoms per alkyl group. Mainly for commercial reasons, the preferred alkyl acid phosphate'is Lorol acid phosphate, which is a mixtureof the phosphoric esters of Lorol alcohol. The term Lorol alcohol is used in the trade to denote a mixture of primary normal aliphatic alcohols of 8 to 12 carbon atoms which are obtained by fractionation of the alcohols resulting from the reduction of cocoanut and/or palm kernel oils. Lorol acid phosphate mixtures are readily obtainable on the market and for this reason are preferred to the more purified esters of greater scarcity and higher price. One Lorol acid phosphate is sold under the trade name Ortholeum 162 and is understood to be mainly a mixture of mono and di acid phosphates of Lorol alcohol. Though for the reasons stated above Lorol acid phosphates are preferred, other alkyl acid phosphates containing from 8 to 16 carbon atoms per alkyl group are satisfactory. Forexample, a commer cial grade of n-octyl acid phosphate was found to produce an excellent reaction product.

, To form the desired neutralization, product, the proper proportions of dihydroimidazole and alkyl acid phosphate may readily be determined by an electrometric titration of a sample of the alkyl acid phosphate with aqueous KQI-I solution to a pH of about 9. From the amount of KQH used the quantity ofamine required to neutralize the acid radicals of the phosphate may easily be calculated. It is always desirable to have a slight excess of amine present, and good results have been obtained with as much as 50% excess of dihydroimidazole.

In order to prevent corrosion effectively, the lower concentration limit of the reaction product with respect to the finished gasoline should be about 0.002% by weight. This was determined by means of ASTM D665-47T corrosion test modified to a bath temperature of 80-82 F. The upper concentration limit is determined by that amount of neutralization product which would cause engine deterioration due to the excessive quantity of phosphates then present. The upper limit is about 0.05% by weight.

Certain embodiments of the present invention are more fully illustrated by the following examples.

Example 1 Into a suitable vessel equipped with means for heating, agitating, and cooling the charge, there are introduced 298 parts of l-propyl, 2-heptadecyl, 4,5-dihydroimidazole followed gradually by 150 parts of a mixture of mono and di Lorol acid phosphates (Ortholeum 162). "he mixture is agitated vigorously and cooled as required to keep the temperature below 200 F. The reaction is vigorous and exothermic, consequently the rate of addition of the phosphate is controlled to avoid exceeding the above temperature limit. The resulting mixture is stirred for-about 1 hour at 140 F. The reaction product is a viscous, oily liquid, yellow in color.

The reaction product is then tested for neutrality by means of the aforementioned neutralization test, and, if found to be acid, additional dihydroimidazole is added.

Finally, five pounds of the finished additive are added to 17,000 gallons of aviation gasoline in a blender and agitated for about minutes. Then 1020 pounds of mixed xylidines are added and the mixture resulting therefrom is agitated for about a half-hour. The final gasoline is completely homogeneous, free from haze, corrosion resistant, and has a rich mixture anti-knock rating commensurate with the amount of xylidines used.

Example II To 17,000 gallons of aviation gasoline in a blender are 4 mono methyl aniline are added and agitation continued for another half-hour. As in the former examples, tests indicate the production of excellent quality finished gasoline.

Although aviation gasolines are used in the above examples for purposes of illustration, and such gasolines may comprise the following:

Alkylate percent 70-88 Aromatics do 5-16 lsopcntane do 5-14 Tetra ethyl lead cc. per gallon 4 nevertheless, the invention in its broadest scope comprehends the treatment of any motor fuel. Similarly, it will be appreciated that the reaction product of the present invention may be blended in proper proportions in any desired gasoline with the advantage that the purchaser or user may add any suitable amount of aniline or homologs thereof, for the purpose of obtaining rich mixture antiknock properties, without difliculties arising from precipitationor haze formation which is generally encountered when less satisfactory corrosion inhibitors are used.

It will now be apparent that I have devised a novel and useful process and composition of matter which embodies the features of advantage enumerated as desirable in the statement of the invention and the above description and while in the present instance there are described the preferred embodiments thereof which have been found in practice to give satisfactory and reliable results, it is to be understood that the same is susceptible of modification in various particulars without departing from the spirit or scope of the invention or sacrificing any of its advantages.

added 5.23 lbs. of l-methyl, 2-heptadecyl, 4,5-dihydroimidazole. The-resultingmixture is thoroughly agitated for about 10 minutes, and then 2.68 pounds of a mixture of mono and di. Lorol acid phosphate (Ortholeum 162) are added with continued mixing for about one-half hour. tion of a satisfactory reaction product, 1020 pounds of After the neutralization tests indicate the produc- I claim:

1. A completely homogeneous, corrosion-resistant aviation fuel, having a high rich mixture anti-knock rating, comprising gasoline containing sufiicient aromatic amine from the group consisting of aniline and homologs of aniline to substantially increase the rich mixture antiknock properties of the gasoline and between 0.002% and 0.05% by weight of the finished gasoline of the addition product resulting from contacting an alkyl acid phosphate having from 8 to 16 carbon atoms per alkyl group With vbetween and of the quantity theoretically required to neutralize said phosphate of an imidazole selected from the group consisting of l-methyl, 2 hep tadecyl, 4,5-dihydroimidazole; l-ethyl, Z-heptadecyl, 4,5- dihydroimidazole; and, l-propyl, 2-heptadecyl, 4,5-dihydroimidazole.

2. The method of simultaneously improving the anticorrosive and the rich mixture anti-knock properties of a gasoline, which comprises forming in said gasoline a corrosion inhibiting amount of the addition product of an alkyl acid phosphate having 8 to 16 carbon atoms 0 per alkyl group and an imidazole selected from the group consisting of 1-mcthyl, 2 heptadecyl, 4,5-dihydroimidazole; l-ethyl, Z-heptadecyl, 4,5-dihydroimidazole; and, l-propy], Z-heptadecyl, 4,5-dihydroimidazole; and in which all the acid hydrogen of said phosphate is neutralized by said imidazole, then adding sufiicient aromatic amine from the group consisting of aniline and homologs of aniline, to substantially increase the rich mixture antiknockproperties. 4 g

3. The method of inhibiting the formation of an insoluble precipitate when an amine-phosphate corrosion inhibitor is added to a gasoline containing an aniline octane booster which comprises adding to a gasoline an alkyl acid phosphate having 8 to 16 carbon atoms per alkyl group, adding between 100% and about-150% of the quantity theoretically required to neutralize said phosphate of an imidazole selected from the group consisting of l-methyl, 2 heptadecyl, 4,5-dihydroimidazole; l-ethyl, -2-heptadecyl, 4,5-dihydroirnidazole; and, l-propyl, 2-heptadecyl, 4,5-dihydroimidazole thereby forming in said gasoline an addition product of said imidazole with said ertles of the gasoline, the amounts of the imidazole and the phosphate being such as to produce an addition prod- 5 uct of between 0.002% and 0.05% by weight of the finished gasoline.

References Cited in the file of this patent UNITED STATES PATENTS Thompson Sept. 29, 1942 Stirton Dec. 24, 1946 Eberz May 1, 1951 FOREIGN PATENTS Germany Nov. 2, 1942 

1. A COMPLETELY HOMOGENEOUS, CORROSION-RESISTANT AVIATION FUEL, HAVING A HIGH RICH MIXTURE ANTI-KNOCK RATING, COMPRISING GASOLINE CONTAINING SUFFICIENT AROMATIC AMINE FROM THE GROUP CONSISTING OF ANILINE AND HOMOLOGS OF ANILINE TO SUBSTANTIALLY INCREASE THE RICH MIXTURE ANTIKNOCK PROPERTIES OF THE GASOLINE AND BETWEEN 0.002% AND 0.05% BY WEIGHT OF THE FINISHED GASOLINE OF THE ADDITION PRODUCT RESULTING FROM CONTACTING AN ALKYL ACID PHOSPHATE HAVING FROM 8 TO 16 CARBON ATOMS PER ALKYL GROUP WITH BETWEEN 100% AND 150% OF THE QUANTITY THEORETICALLY REQUIRED TO NEUTRALIZE SAID PHOSPHATE OF AN IMIDAZOLE SELECTED FROM THE GROUP CONSISTING OF 1-METHYL, 2 HEPTADECYL, 4,5-DIHYDROIMIDAZOLE; 1-ETHYL, 2-HEPTADECYL, 4,5DIHYDROIMIDAZOLE; AND, 1-PROPYL, 2-HEPTADECYL, 4,5-DIHYDROIMIDAZOLE. 